Why are the Indus dolphins endangered
The Indus dolphin (Platanista minor) counts within the family of the Ganges dolphin family (Platanistidae) to the genusPlatanista. In English, the type Indus River Dolphin, Susu, Indus Dolphin called. The species is monotypic, so no subspecies are known (Wilson & Reeder, 2005).
Originally Ganges dolphins (Platanistidae), River dolphins (Iniidae) and Chinese river dolphins (Lipotidae) run in a family. However, genetic studies have shown that they form a convergent group of only distantly related species that are only superficially similar. Common features are, for example, the rudimentary eyes. However, this feature has developed independently. The reason for this is likely to be the similar habitats. Today it is assumed that Ganges dolphins (Platanistidae) evolved from the early toothed whales during the Oligocene. This was the case around 30 to 35 million years ago. The unanimous opinion is that the Ganges dolphins have moved away from the Sperm whales (Physeteridae) split off, the Chinese river dolphins and the river dolphins (Iniidae) of the Beaked whales (Ziphiidae) and Porpoises (Phocoenidae).
Appearance and dimensions
The Indus dolphin reaches a body length of 150 to 250 cm and a weight of around 70 to 80 kg. Males stay smaller and lighter than females. A striking feature is the long beak with the broadened tip. It reaches a good 1 fifth of the body length. In the beak there are 26 to 39 pairs of large, conically shaped teeth per jaw. The dorsal fin is small and lies just before the base of the tail. Both the pectoral fins and the caudal fin are large and wide. The dorsal skin is dark gray to gray-brown in color, anteriorly it is clearly lighter in color. The forehead is steeply sloping and ends at the base of the beak. The melon is rounded. The eyes are small and of a rudimentary character. Since there are no lenses in the eyes, the sense of sight is very poorly developed (Novak, 1999).
Way of life
Indus dolphins usually live solitary or in pairs. When foraging for food, the animals usually go solitary. Larger schools of 10 to 30 individuals are very rare and can only be observed in habitats with sufficient food. Orientation, foraging for food and, to a certain extent, communication with one another take place exclusively via echolocation. The animals cannot distinguish colors with their sense of sight. Ultimately, you see everything in grayscale. Indus dolphins are relatively slow and sedate swimmers. The dives last an average of 90 seconds. However, dives lasting several minutes are also known and can reach depths of 6 m. When searching for food, the sediment on the bottom of the water is rummaged with its long beak and food is found. During the dry season from October to April, there are usually larger hikes into deeper waters, as the water levels drop significantly at this time. In particular, tributaries are avoided during this time (Novak, 1999).
distribution and habitat
The Indus dolphin is endemic to Pakistan. Historically, the species was distributed in the entire river system with a length of about 3,500 km. Today the animals can be found on a small part of 700 to 1,375 km of the river, depending on the author. The deposits mainly extend between the Sukkur and Guddu barrages in Sindh Province. Smaller populations live between the Chashma and Taunsa barrages and in the Punjab Province in northeastern Pakistan. Indus dolphins colonize freshwater rivers. You mainly meet the animals in the deep main waters, during the rainy season also in shallower tributaries. In 2008, a small population of 10 to 15 dolphins was discovered in India in the Beas River. The current total population (5 subpopulations) is estimated at 1,200 to 1,340 (IUCN, 2014; Awan & Shah, 2012).
Indus dolphins feed mainly on fish (Osteichthyes), Shellfish (Bivalvia), other molluscs (Mollusca) and crustaceans (Crustacea). To a small extent, according to the unanimous opinion, turtles (Testudinata) and Birds (Aves) eaten. The food is usually explored at the bottom of the water and is carried out by echolocation (Novak, 1999).
The gestation period is unknown, but it is estimated to be 8 to 11 months. Births can occur throughout the year. However, the peaks are between December and May. A female gives birth to a young and is suckled for a good year. At birth, the offspring are 80 to 90 (80) cm in length. Sexual maturity is reached with a length of about 170 cm. As a rule, the first mating occurs between the ages of 6 and 10 years. Life expectancy under favorable circumstances in the wild is 30 years (Novak, 1999).
Ecology, hazard and protection
Indus dolphins are one of the most endangered species today. In the IUCN Red List, the species is listed in the EN, Endangered category. The Washington Convention on Endangered Species lists the Indus dolphin in Appendix I of the agreement. The greatest dangers include the destruction of natural habitats, in particular fragmentation through barrages, catching, unwanted bycatch, extensive water pollution and deliberate killing (IUCN, 2014).
The animals were hunted heavily in the past. The bacon, from which oil was extracted, was processed. The meat of the animals ended up in the traditional meat markets. Even if hunting is forbidden today, poaching continues in the absence of controls. Bycatch in traditional fishermen's nets is also a problem. However, the number of losses from bycatch is not clearly documented. For fishermen, the Indus dolphin is a food competitor. Therefore, it is deliberately killed in large parts of the distribution area. Not to be neglected is water pollution from industry, agriculture and settlements. Mercury and arsenic in particular are proven. Pesticides get into the water through agricultural fertilization. Another major problem is the fragmentation caused by barrages. In particular, electricity is generated at the barrages. Populations are isolated by the barrages, a genetic exchange between the populations can no longer take place. Small subpopulations are also susceptible to external influences. Migration is blocked by the existing barrages (IUCN, 2014; Waqaset al, 2012).
- Main Products: Whales (Cetacea)
Literature and sources
- Ronald M. Nowak: Walker's Mammals of the World: v. 1 & 2. B&T, edition 6, 1999, (engl.) ISBN 0801857899
- Don E. Wilson & DeeAnn M. Reeder: Mammal Species of the World, a Taxonomic & Geographic Reference. J. Hopkins Uni. Press, 3rd ed., 2005 ISBN 0801882214
- David Macdonald: The great encyclopedia of mammals. Ullmann / tandem ISBN 3833110066
- Hans Petzsch: Urania Animal Kingdom, 7 Vols., Mammals. Urania, Stuttgart (1992) ISBN 3332004999
- Mammals. 700 species in their habitats. Dorling Kindersley, 2004. ISBN 383100580X
- Hadoram Shirihai, Brett Jarrett: Marine Mammals - All 129 species worldwide. Kosmos, Stuttgart, 2008
Qualified web links
Page categories: Ganges dolphins
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